New posts in Cohomology

Complement to a union of spheres in a sphere

Oriented cobordism classes represented by rational homology spheres

A nontrivial principal bundle which satisfies Leray-Hirsch theorem

The homology of the universal covering space, why so difficult to compute

Motivating the coefficient field of $\ell$-adic cohomology

An intuitive explanation for group cohomology via cochains?

Unifying "cohomology groups classify extensions" theorems

$d^3$ in the Atiyah-Hirzebruch spectral sequence for (twisted) $KO$

Image of a map on cohomology rings

What is the $\mathbb{Z}_2$ cohomology of an oriented grassmannian?